The present invention is concerned with the use of high impact polystyrene for the inner container and outer cup. High impact polystyrene is styrene which is reinforced during the polymerisation process by the addition of synthetic rubber such as polybutadiene or butadiene styrene rubber. Depending upon the rubber content, the resulting high impact polystyrene can be rigid in nature (low rubber content) or elastic in nature (high rubber content). The elastic limit of a high impact polystyrene therefore varies in accordance with the rubber content. A commonly used method for indicating the impact resistance and elasticity is the Izod. Impact measurement, and the characteristics of the high impact polystyrenes used in the present invention are expressed in terms of the Izod Impact Measurement.